Dual Partial Field Stops for EUVL Exposure Uniformity
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Solution Overview
Problem
Conventional EUVL exposure apparatuses face challenges in maintaining uniform exposure amount distribution and suppressing adverse effects on image formation due to the placement of field stops in reflection type optical systems, which can project field stops onto the photosensitive substrate, making it difficult to achieve consistent exposure.
Innovation Solution
The illumination optical apparatus is designed with a first partial field stop positioned farther from the mask than a second partial field stop, allowing for improved uniformity of exposure amount distribution while minimizing the adverse impact on image formation by adjusting the distances and shapes of the field stops.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the second partial field stop is positioned close to the mask to minimize light blocking, then the adverse effect on image formation is reduced, but the first and second partial field stops are projected onto the photosensitive substrate making exposure amount distribution non-uniform
Solution Approach 1:
The field stop is divided into two separate partial field stops: a first partial field stop positioned farther from the mask and a second partial field stop positioned closer to the mask. This segmentation allows each partial field stop to serve different functions - the first defines the outer edge of the illumination region while the second limits reflected light, thereby resolving the contradiction between minimizing light blocking and maintaining exposure uniformity
Solution Approach 2:
The patent positions the first and second partial field stops at different distances from the mask along the optical axis, creating a three-dimensional arrangement rather than placing both on the same plane. This dimensional separation prevents both field stops from being projected onto the photosensitive substrate simultaneously, thereby maintaining uniform exposure amount distribution while still effectively limiting light
2Ease of operation
If the field stop is positioned on a plane parallel to the mask near the mask to define the static exposure region, then the exposure region is properly defined, but the field stop blocks part of the light carrying mask pattern information
Solution Approach 1:
Different regions of the optical path are assigned different field stop elements with specific functions: the first partial field stop (farther from mask) defines the illumination region boundary, while the second partial field stop (closer to mask) specifically limits reflected light. This localized functional assignment allows effective exposure region definition while minimizing unnecessary light blocking
Solution Approach 2:
The first partial field stop acts as an intermediary element positioned between the light source and the mask, defining the illumination region before light reaches the mask. This intermediate positioning allows the system to define the exposure region without requiring the field stop to be immediately adjacent to the mask, thereby reducing light blocking of pattern-carrying beams
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This configuration effectively suppresses the adverse effects of field stops on image formation and enhances the uniformity of exposure amount distribution, enabling excellent exposure conditions for semiconductor and other device manufacturing processes.
Implementation Method 1
a first partial field stop to limit a light beam traveling toward the first surface
Implementation Method 2
a second partial field stop to limit a light beam reflecting from the reflection type original plate
Implementation Method 3
illumination optical apparatus for illuminating a second surface optically conjugate with a first surface via a reflection type original plate
Data Source
AI summary
There is disclosed a illumination optical apparatus for illuminating a second surface optically conjugate with a first surface via a reflection type original plate which can be arranged on the first surface, the illumination optical apparatus comprising: a first partial field stop arranged to define a first outer edge of a illumination region which is to be formed on the second surface, in order to limit a light beam traveling toward the first surface; and a second partial field stop arranged to define a second outer edge of the illumination region, in order to limit a light beam reflecting from the reflection type original plate which can be arranged on the first surface, wherein a first distance between the first partial field stop and the first surface is set to be larger than a second distance between the second partial field stop and the first surface.